1. Field of the Invention
This invention relates to the door lock art and more particularly to an improved security door lock providing signal information indicating the unauthorized opening of a door.
2. Description of the Prior Art
Security devices are often utilized in various door lock arrangements to protect the privacy and/or contents of businesses, homes apartments and other places. Such security devices as incorporated in doors have often been intended to prevent the unauthorized entry into the premises protected by the security device since conventional door locks including handle operated latching structures and deadbolts can usually be forced or otherwise rendered inoperable. That is, conventional handle operated latches can often be forced open by the insertion of a rigid prying tool or even a stiff plastic such as a credit card between the door and the jamb to force the latch into a retracted position. Even deadbolts can be cut by the insertion of a sawing instrument between the door and the jamb and cutting, through the deadbolt. Further, many alarm devices incorporated into the conventional door lock structures have often been comparatively complicated and/or expensive structures not adapted to the requirements for mass production and installation.
In U.S. Pat. No. 3,402,405 there is shown a self locking burglar alarm system which uses a spring biased bolt arm extending across and through opposite walls of a housing. An audible alarm and switching means are also located in the housing. One end of the bolt arm engages a latch plate near an opening while the other end is used to move the arm back to extend the spring to cock the arm. When the window or door upon which the alarm is mounted is moved, the end of the arm moves from the latch plate into the opening to provide a lock. At the same time the arm actuates the the switching means to trigger the alarm. The device as so disclosed has several disadvantages. First of all, the structure does not lend itself to mass manufacturing and installation techniques to produce a heavy duty lock. Also, since the end of the arm opposite the one engaging the latch plate extends out of the housing, it can be reached through an adjacent window to disable the alarm. Further, the cooperative relationship between the operative end of the bolt arm and the latch plate are such that it is possible for an intruder to move the bolt arm to an inoperative position from outside the area to be protected.
Many other mechanical and/or electromechanical security devices have been proposed for incorporation into security devices for various purposes. However, a security device operated by magnetic forces has not heretofore been available for inclusion in mass production and installation techniques.
In U.S. Pat. No. 2,193,488 there is shown a refrigerator lock mechanism with a switch to activate the light within the refrigerator. No magnetically operated structure is provided. In U.S. Pat. No. 3,770,930 there is shown a safety switch for a microwave oven which employs an irregular shaped actuator that only allows power to turn on when the microwave door is closed and the actuator is meshed.
In U.S. Pat. No. 3,851,325 there is shown a lock and alarm structure utilizing a spring and a bolt. An alarm 66 is also provided with batteries in the lock housing. In the armed position, if the door is moved, the bolt slips from a shoulder and the spring pushes the bolt forward to activate the alarm. In U.S. Pat. No. 4,248,463 there is shown a security system with a dead bolt lock and sensing and control means for sensing whether or not the lock is in the locked position. Means are also provided to activate and deactivate the alarm and also to utilize an information signal generated by the structure to operate an electric appliance. In U.S. Pat. No. 5,257,841 there is disclosed an electrical lock strike device to monitor whether a deadbolt is present or not.
In none of the prior art patents is there even shown or suggested the use of a magnet with the attendant use of magnetic forces to provide the actuation of an alarm system. Thus, there has long been a need for a magnetically operated security lock which can be conveniently incorporated into existing lock structures for mass production and installation without requiring major rework or rededsign of the basic lock structure.